Under what circumstances is the audio connection from the Maestro RR to the Pioneer head unit's Aux In port needed?

I have a 2012 Highlander without JBL. I have an aftermarket panel mount AV aux port (i.e. including video) from a previous installation that has a 3.5mm plug on the end that goes into the radio. If I need the Maestro audio connection into the head unit, then I'll have to get an adapter to convert the 3.5mm plug to three RCA plugs for connecting to the AV Input. If I don't need it, then I can simply plug it into the radio's Aux In jack.

In most cases, the audio cable from the RR has to plug into the aux to allow the audio from OEM sources to play. This is because Pioneer does not give us a dedicated audio input for when we retain those things. However, in your case, because you aren't retaining any OEM sources that require audio transfer you actually don't need to use this audio cable.

Because of that, you can take the AUX on the TO1 harness, adapt it, and plug it directly into the aux of the radio.

I'll just plug my existing Aux plug directly into the head unit then. As I recall, the audio from the Maestro RR is on a dedicated three-pin connector on the unit, so I'll just leave it disconnected on both ends.

Is the T01 harness wired up to provide power to the terrestrial radio antenna amplifier? I'd rather not tear the dash apart again to find out. According to the wiring diagrams for my vehicle from Chilton, the power appears to be on pin 8 of connector E8, which is the same connector that contains the power and front speaker connections, so it should be available to the T harness.